How to use the @lumino/domutils.Platform.IS_IE function in @lumino/domutils

if (previousWidget) {
      previousWidget.hide();
    }

    // Show the current widget.
    if (currentWidget) {
      currentWidget.show();
    }

    // Emit the `currentChanged` signal for the tab panel.
    this._currentChanged.emit({
      previousIndex, previousWidget, currentIndex, currentWidget
    });

    // Flush the message loop on IE and Edge to prevent flicker.
    if (Platform.IS_EDGE || Platform.IS_IE) {
      MessageLoop.flush();
    }
  }

restoreLayout(config: DockPanel.ILayoutConfig): void {
    // Reset the mode.
    this._mode = 'multiple-document';

    // Restore the layout.
    (this.layout as DockLayout).restoreLayout(config);

    // Flush the message loop on IE and Edge to prevent flicker.
    if (Platform.IS_EDGE || Platform.IS_IE) {
      MessageLoop.flush();
    }

    // Schedule an emit of the layout modified signal.
    MessageLoop.postMessage(this, Private.LayoutModified);
  }